Sag indicator



F. A. E. KOSKI Dec. 6, 1955 SAG INDICATOR 3 Sheets-Sheet 1 Filed June 1, 1951 INVENTOR F. A. E. KQSKI SAG INDICATOR Dec. 6, 1955 3 Sheets-Sheet 2 7 Filed June 1, 1951 INVENTOR (9.. a 5XOAL ATTOR EY United States Patent Qfiice 2,725,843 SAG mnrcA'ron Francis A. E. Koski, Snow Shoe, Pa. Application June 1, 1951, Serial No. 229,433

4 Claims. or. 116-114) My-inventionrelates broadly to mine safety appliances and more particularly to a sag indicator which may be installed in the roofs of mines for indicating theprogressive condition of sag in order to predetermine any dangerous condition of mine roof failure.

. One of the objects of my invention is to provide a construction of sag indicator which may be installed in mine roofs at variouslevels below the earth for providing accurate' means" for inspection andmeasurement of any changein sagof the mine roof for providing a predictable indication of dangerous conditions of roof failure.

Another object of my invention is to provide a constriuction of warning indicator for mine roofs which may be' i-eadily installed in a mineroof in a manner in which the indicator is reliable forsounding an alarm under conditions of dangerous sagging of'the roof for enabling preventative measures to be taken ,atvery early stages of roof sagging for avoiding collapse of the roof. ,Another object of my invention is to provide a construction of sag indicator which is so inexpensive that large numbers of such indicators may be installed in various parts of the roof structure of a mine for enabling periodic inspections to be made of sagging conditions of the roof for predicting dangerous conditions of the roof and enabling precautionary me'asures to be taken for preventing roof failure by the installation of supplemental timbers or bracing means.

' Still another object of my invention is to provide a simplified construction of calibrated sag indicator for installation in mine roofs by which a calibratedindicator may be inspected from time vto time for predetermining the condition of sag of the mine roof to enable preventativemeasures to be taken at the very early stages of any indication of mine roof failure;

' Stilljanother object of my invention is to provide an arrangement of dependable electric circuit closer which is operative under conditions of sag of a mine roof for sounding an alarm for providing'an indication of dangerous roof condition to enable proper reinforcement to be made at indicated dangerous locations in the mine for improving mine safety conditions.' 7 7 Other and further objects of my invention reside in a simplified construction of sag indicators for installation in mine roofs as set forth more fully in the specification hereinafter following by reference to the accompanying drawings in'which:

'Figure 1 illustrates a coacting pair of sag indicators constructed in accordance with my inventionand installed in spaced positions transversely of the center of a mine roof in positions where shear slippage or sagging adjacent the center of the roof may differentially alfect either of the sag indicators; Fig. 2 is a view looking upwardly of the floor of the mine and showing the sag, indicators ininstalled' position in the roof of the mine; Fig. 3 'is'a horizontal sectional view taken on line 33 of Fig. 1; Fig. 4 is an enlarged view similar to the view shown in Fig. 1 but illustrating a condition of sag in the mine'roof and the manner in which this condition is at once made apparent upon inspection of the sag indicator of my invention; Fig. 5 shows a modified form of the device for measuring sag constructed in accordance with the principles of .my invention, the resilient means for separatingthe measuring plates being omitted in this instance for purposes of simplification; Fig. 6 is a perspective view of one of the measuring plates used in the form of sag indicator illustrated in Figs. 1-5; Fig. 7 is a perspective view of a modified form of one of the measuring plates; Fig. 8 is a plan view of a form of resilient separator which may be employed for. initially maintaining the measuring plates in spaced relation; Fig. 9 is a transverse sectional view taken on line 9- 9 of. Fig. 8; Fig. 10 is a plan view of a further modified form of resilient separator for the measuring plates; Fig. 11 is a side elevational view of the spring separator shown in Fig. 10; Fig. .12 .is a vertical sectional view taken through a further modified form of sag indicator of the self-indicating type in which an indicating needle is displaced over a calibrated scale in accordance with displacement of the position of the meas uring plates under varying conditions of sag, the resilient means for maintaining the measuring plates in spaced relation being also omitted in this instance for purposes of simplification; Fig. 13 is a vertical sectional view taken on line 1313 of Fig.12; Fig. 14 is a schematic and diagrammatic viewwith parts broken away and shown in section and illustrating an electric alarm signal controlled bythesagindicator; Fig. 15 is an enlarged vertical sectional view of the electric alarm device illustrated in Fig. 14 and showing the components by which an electric circuit is closed due to conditions of sag of the mine roof structure; Fig. 16 is a transverse sectional view taken on line 16-16 of Fig. 15; Fig. 17 is a horizontal sectionaljview taken on line 17-17 of Fig. 15; Fig. 18 is a view illustrating the condition resulting from sagging of the roof structure and the closing of an electrical circuit through the contact members associated with the form of my invention illustrated in Figs. 14-17; Fig. 19 illustrates a further modified form of sag indicator embodying my invention; and Fig. 20 is a perspective view of themeasuring element employed in the form of my invention shown in Fig. 19.

My invention 'is directed to safety systems for mines in which dangerous conditions of roof failure may occur without knowledge or warning and the failure reach such proportions that remedial steps for reinforcement of the mine roof may, be too late.- The hazards of roof failure are continually increased in mines due to blasting in adjacent areas and conditions of shear-and sag in the roof often reach dangerous proportions before the slippage is discovered bringing about a condition of great peril to the mine workers. It is recognized that mine roofs do not fail without warning and if a warning can be given sufiiciently in advance of a dangerous condition of sag ample time is available for the erection of supporting timbers or beams or suspension rods for bracing or reinforcing the roof to prevent failure. The sag indicator of my invention greatly simplifies detection and measurement of roof sag. My invention provides means for indicating the rate at which the sag may be progressing and thus allows the condiiton of the invisible layers. The indicator of my invention shows the extent of the roof fall in time to allow preventative measures to be taken such as the timbering or the installation of suspension rods and allows for their economical installation by determining the amount of reinforcement required to prevent sag. The sag indicator of my invention is not limited to applications of mining but can be used in construction work generally such as in connection with concrete forms and the like. The sag indicator is constructed in multiples so that the condition of one indicator may be compared to the condition of an adjacent indicator. Each Fatented Dec. 6, 1955v indicator comprises" a suspension rod which is anchored into thestrata of the mine roof or thematerialof abeam. The suspension rodcarries a pair of measuring plates having means therebetween for normally separating the plates. A variety of different means-maybe cm-' ployed for this purpose, such-as coil-springs, compressible, resilient or yieldable material and/or leaf springs. These spring devices normally tend to maintain the measuring platcsin predetermined spacial relation. However, con-- ditions of sag in one area of a roof or beam structure may affect movement of one measuring plate toward a coacting measuring plate differently'than' conditions existing with-respect to the measuringplates-ofan adjacent indicator. This differential distance is readily measurable to indicate the conditions which may be predicted'with regard to displacement in the invisible strata of a mine roof structure for thereby indicating'dangerous conditions" of sag. In certain instances the'indicator is calibrated to show the progressive movement in the invisible strata of the roof structure. In other instances-the separator between the measuring plates includes electrical contactors which may be displaced to close an electrical circuit and thereby supply a warning alarm. All of these indication means enable remedial steps to be taken for reinforcement of the mine roof structure for preventing fur-- ther sagging at dangerous'locations'. 7

Referring to the drawings in more; detail reference characters 1, 2, 3, 4; 5, 6; 7 and 8 in Fig; l'indicate the strata-constituting a mine'roof, the superimposed layers of which aresubject to sagging, slippage and shear and into'which the holes 11 and 12 are drilled. These drill holes-are generally selected in susbtantially' the center of the span ofthe'roof structure-in" a mine where conditions of sag are most likely to occur; Suspension rods" 14-and15 are driven intothe drilled holes" 11 and 12. Thesuspension rods are each provided with a spike end as represented at 14a and 15a for accurately fastening the suspension rods in the strata of the roof structure. The

suspension rods are screw threaded on the'endsthere'of as'represented at 14!) and'15b. A measuring plate 16 is slipped-over the screw threaded end of suspension rod'14 and is loosely retained on the suspension rod while the compressiblemember such as a coil'spring', a leaf spring.

or a compressible block of material is'vertically'moved into position over the" suspension ro'd. In the form of my invention illustrated in Figs; L4 this compressible member is in the'form of a co'ils'pring 17. Thefcoil.

spring is retained in position by"mea'ns' of a measuring.

plate 18 which is slipped over the end of the suspension rod 14 within the limitsof the'screw'threaded portion 14b of the suspension rod. An adjustable securing nut I? is engaged. over the screwthreads 14a on the" end of the suspension rod 14 for confining'the compressible member 17 between the measuring'plates' 16a'nd"18.' Tension. is applied to" the compressible member 17 'byinitially a'd justing nut 19 to a position in" which the initial measurement -as the device is installed maybe" detcrminedby the" distance=AasshoWn-in' Fig.- 4. A suitable lo'ck' nutmay be ap Iied tO-the threaded'end 14'bofsuspension rod-14' for insuring the precision'maintenance of the initial-setting of: the-spacial relation of the measuring'plates'z' On: the adjacent suspension rod 15 with which" the measurements revealed by"'the spacialrelation of. the measuring: plate 16 and 18- onsuspension rod'14fareto be compared, I provide a similar arriangementof'measur ing plates spacially separated by a substantially identical compressible member and secured in position bya suitable-nut. This arrangement issho'wnat'theright ofFigs. l and 4 of thedrawings where the measuring p'late'which' directly contacts the lowermost strata ofth'eminero'of' 18- indicated at-.2(ilo'osely fitting over suspensionrod lsand. maintained in position by compressiblemembe'r 21' against which measuring'plate 22 is confined by'meansof suitable nut 23 engagedover screw threads 15a on the end of the suspension rod15. The compressible mem- 4. bers 17 and 21 and all of the associated parts of the sag indicators are held within close tolerances -so that opcrat-- ing characteristics for all indicators are substantially the same. The spacial distance between measuring plates 20 and 22 is initially set to be identical with the spacial distance between measuring plate 16 and 18 of the adjacent indicator when installed. The sag indicators when installed may continue to" showlthe same special distance between measuring plates 16 and 18 and measure plates 29 and 22, for example, for all normal conditions in the roof seams 18 in Fig. l or-"1--10 in Fig. 4. The spacial distance between measuring plates 16 and 18 or between measuring plates 20 and" 22 may be checked from time to time with a suitable measuring device such as a caliper or appropriate scale and for all normal conditions there may be no variation in the spacial relation of the measuring plates as revealed by these periodic checks and measurements.

Howeven as' shown inFig. 4sag'ging may occur'in the roof scams 3, 4,' 5, 6', 7, 8, 9 and 10, to the right of the center ofthe roof span and ash'earingmay occur along the center line" designated at 24 in Fig. 4 insuring in the dropping of an unsupported'area' of the roof structure with respect to the supported area of the roof structure as' slio'wnin Fig. 4'. This sagging may or may'notbe' observable to'- the eye'but produces a displacement of the roof seams for a distance indicated by distance C in'Fig. 4'. This slippage results inthe movement of measuring: plate 20tow'ard measuring 'plate 22 onsuspension rod 15 with'intheunsupported area of the mine" roof resulting in' compression of the compressible member 21 so that: measuring plates' 20 and 22' approach each other to the distance B. Thus a perceptible ditference' in spacial relation between measuring plates 16' and 18 and measuring plates 20 and22 is" readily observable by measurement of the distance B between measuring plates 20 and 22. as compared'to the distance.A between measuring plates 16' and 18. Upon discovery of the differential measurement remedial measures may be taken to reinforce the unsupported area of .the'mine roof by timbering, bracing, and/or the installation of additional suspension rod's for reinforcing the roofa'nd-preventing further sagging. It isreadily'apparent'that without such a precautionary indicatora'sprovided' by'my invention sagging of the mine. roof in various areas might go unnoticed and only be discovered aftera condition bordering upon collapse of the mine ro'oflex'ists which-might be-too late for correction.

Various arrangements. of .rneasuring means may be providedand'in Fig'. 5 Ihave illustrated an arrangement in which the measuring, plates 20 and 22 supported on sus' pension rod 15are each provided with precision measur-- ing points 20a and 22a which are screw threaded or. riveted? into the measuring plates 20 an'd22 in alignedpositionsi adjacent one edge thereof. The measuring points: 20a and22a servetas surfacesbetween which. the measur-. ing arms-25' and 26 of Laisuitable' telescopic. micrometer. ga'ge'27ma'y' be inserted. The. micrometer gage 27 car ries appropriate calibrations28 on the adjustable seale thereof by which the spacial'relationof the arms 25 and 26 which pivot about center 29 are madequickly available. Thus the spacial distance between measurement plates ,20 'and'22 may bequicklychecked at-each. of-the indicator installations and differences in thespacial rela tion ofthe measuringplates quickly detected. For purposes of simplification, I'have omitted the arrangement ofcompressible member between measuring plates 20 and- 22 in Fig. 5 but it will be understood that such compi-essible member may be a coil or leaf spring or a spacer formed-from resilient or yieldable material.

' In Fig. 6.1. have. shown. in perspectiveview the..form.: of mea'sure plate .I6?.which m: .y. bezemployeddn tbedndi cato'r'oflmyinventiom Fig. I shows.-still-another.form' of :measuring plate-such as circular plate 30 which'm'aytlbe employedin the sag indicator of my invention.

In Figs. 8-and 91- have shown a construction-ofresilient or yieldable block 31 which may be used as a separator between the measuring plates in the sag indicator. Thisblock may be. formed from rubber or yiedable synthetic composition sufiicient to maintain the normal spacial relationxof the measuring plates but sufficiently yieldable to allow displacement of the material under conditions of compressive force. Figs. and 11 show a form of leaf spring which I may employ in association with the suspension rod as a spacing device for the measuring plates on the suspension rod in lieu of the coil spring of Figs. 1-4 or the block of Figs. 8- and 9-. I have shown the leaf spring at 32 having a central elevated portion apertured at 32a for the passage of the suspension rod andhaving a'pair of outwardly extending downwardly directed spring arms-32b and 32c.

The centralportion of the-leaf spring bears against the upper measuring plate while the spring arms 32b and 320 bearagainst .the bottom measuring platefor yieldably maintaining the: measuring plates in separated relation throughout the period when the-upper measuring plate is approaching the lower measuring plate, under conditions of'sag. s f

In Figs. 12 and 13 I have shown a sag indicator embodying my invention where the indicator is of the selfindicating type. In this arrangement the suspension rod 15 is shown extending through measuring plates and 22 in a position below the roof structure 9-10 of the mine or other structure in which the condition of sag is to be detected. The terminating end of the suspension rod 15 is screw threaded as shown at 15b and is engaged by nut 23 for maintaining measuring plate 22 in position. The measuring plate 22 carries the vertically extending indicator plate 33 which is welded at its lower edge to the upper face of measuring plate 22 as represented at 34. The indicator plate 33 carries a calibrated scale 35 thereon which is graduated to show various conditions of sag directly observable by movement of the pointer 36 over scale 35 as the condition of sag increases. Pointer 36 is pivotally mounted in the upper left-hand corner of indicator plate 33 as represented at 37 and is provided with an extension 38 thereon with an upwardly extending projection which establishes tangential contact with the undersurface of measuring plate 20. A lever arm is thus provided between the extension 38 of the pointer 36 and the central pivot 37 so that as measuring plate 20 approaches the limiting edge 33a of the indicator plate 33 pointer 36 is moved over the range of the calibrated scale 35 visually indicating the condition of sag in the mine roof. It will be understood that the compression coil spring such as coil spring 21 of Figs. 1-4, or the resilient spacer 31 of Figs. 8 and 9 or the leaf spring 32 of Figs. 10 and 11 is provided in the structure of Figs. 12 and 13 for maintaining the measuring plates 20 and 22 in spaced positions so that measuring plate 20 will follow the actual sag condition of the mine roof or other structure.

In Figs. 14-18 I have illustrated another embodiment of my invention in which an electrical circuit is closed for sounding an alarm under conditions of sagging of the mine roof or other structure. In this arrangement a resilient body 39 is provided for normally spacing the measuring plates 20 and 22 where the suspension rod 15 passes through the resilient body 39. The resilient body 39 is vertically apertured adjacent one side thereof as represented at 40 for receiving spaced contact plugs 41 and 42. The spaced contact plugs snugly fit into the resilient bore 40 and are provided with contact faces 41a and 42a thereon which are normally spaced apart under normal and safe conditions with respect to roof sag such as the condition illustrated in Figs. 14-16. The contact plug 41 connects through electrical conductor 43 insulated as shown at 44 and electrically connected to an alarm circuit represented at 45 in Fig. 14 including the electric signal device 46, and a source of potential 47 electrically connected to ground as represented at '48. The contact .sag of theroof structure measuring plate 20 moves tocompressing the resilient body' ward measure plate 22 39 to the dimension Y as represented in Fig. 18 thereby compressing contact plug 41 with respect to contact plug 42tclosing an electrical circuitthrough contact faces 41a and '42a and through the-grounded return path 4948 for operating the electric signal device 46. To facilitate the establishment of a good electrical connection between contact plug 42 and the measuring plate 22 the contact plug 42 is provided with a conical shaped end 42b which tends to enter the surface of measuring plate 22 insuring a-good electrical connection therewith. Thus the ap-' proach of measuring plate 20 toward measuring plate'22 under conditionsof dangerous sag isdetected by the sounding of either an audible or a visual alarm by electrical action.

In the several forms of my invention the confining nuts 19 and 23 have been indicated as engaging the screw threaded ends of the suspension rods. It is to be understood that lock nuts may be provided in these positions to prevent shocks or vibration from dislodging the nuts 19 and 23 and thus impairing the operation of the indicator of my invention.

Figs. 19 and 20 illustrate a form of my invention in which the measuring plates are omitted and a resilient strip 50 bent into the shape of a U with the flat ends of the two arms thereof provided with apertures 51 and 52 which when aligned permit the bent strip to be positioned over the depending end of the suspension nut 15b, so that the projecting ends of the two arms of the strip are free to be compressed toward each other as the structure, such as 7, 8, 9, and 10, develops a condition of sag. The upper flat face of the top arm of the U shaped strip 50 directly bears against the lower surface of the strata 10 and is bent toward the lower flat face of the lower arm as the strata 10 is displaced downwardly. The distance 53 between the projecting ends of the arms of the strip may accordingly be measured to determine the condition of slippage of the structure 7, 8, 9, and 10. Nut 15b may be initially adjusted on the screw threaded end of the suspension rod 15 for fixing the spacial relation of the ends of the arms of strip 50 to a normal position with respect to which the approach of the ends of the arms may be compared from time to time for determining the amount of sag in the associated structure.

I have described my invention in certain of its preferred embodiments but I realize that modifications in structure and arrangement may be made and I desire that it be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What 1 claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A sag indicator comprising a suspension rod adapted to be anchored in a structure for which the condition of sag is to be determined and projected downwardly therefrom beyond the lower surface of the structure, a U shaped resilient strip bent upon itself and having aligned apertures therein adapted to be positioned over the depending end of said suspension rod with the upper surface of one arm in contact with the surface under observation for the condition of sag, and means attached to said rod for confining the position of the other arm of said U shaped strip whereby the ends of the arms of said strip approach each other as the condition of sag in the structure under observation increases.

mamma- 2. Sag. indicator as? set forth: in: claim 1; inlwhieh the: terminating; end: oflsaid: rod iSiSCFW threadedaandl whereinwsaidtthreads are -engaged by! alscrevtt threaded nut-tadiustable against the-bottom su'r face of the lower arm ofsaid strip fon initiallyt settings thespatial: relationof: theends" of said :arrns and for subsequently observing the approachtof theyends-ofi said: arms for correspondingly determiningithe condition ofi sag ofi said structure." 3. Apparatus. for warning, of? failure of: a roof having; an opening: extending; upwardly" therein comprising, a rod-having itswupper end secured to the roof= at the inner endvof said opening. and its-'lower end terminating; ad jacentthetouter end-ofsaid opening; atbowed resilientstrip of material having; free lineally; disposedsendstextendingsubstantially paxallel to each other iand:-'terti1inat-:

ingin substantially: lineal end-edges' andpositionedover the dependingendsofi. saidvrod :with thebowedi portion of said strip proicctingt laterally; witht respect-Mo :one side 10L said -rod and-.the free. endsroftsaid strip projecting. laterally? inthe opposite direction with: resp'jeev to the* otherfside ofi said rod,=-and me'ansiattaehedrto'said rod for confining: s'aidbowed strip-thereon: with-one ohtheefree endsaof'- said strip.- maintainedin contact with' the lowensurface' of thereof: underlobse'rvation and: the other fre'etentl of- Sil'idiStIifl-bifiSCd to a position against= said manfinlhc resiliency; of" said strip :being such thatslippage pressure oithe roof againstthefirst mentioned ftee endof-- said strip, operates tomo've the said free; end of said stribr in 1 tioned free end-ofsaid-bowed-strip for initially adjust-1 ing the' spatial relation ofthe free endsofsaid strip prior to. a condition of failure of the roof.

References Citedin thefile'o'fthis patent UNITED STATES PA'IEII'I'S 1,018,328 Lee" ef-a1. .i.' Feb; '20, 1912 1,737,514 Nikolish NOV. 26,- 1 929 

